Abstract: Apparatus for balancing a rotating body in which the body is mounted for rotation and operatively coupled with a mechanism for rotating the body. Sensor means coupled to the rotating body transmit an unbalance signal in response to unbalance of the body to control means which compute the amount and location of compensating material required to be removed from the body in order to balance the body. Machining means for removing the computed amount of compensating material comprises a laser positioned to direct a laser beam at a rotating mirror synchronized to the rotational speed of the rotating body. An annular stationary reflector is positioned coaxially with the rotating mirror and is adapted to reflect the laser beam received from the rotating mirror to the rotating body thereby ablating the compensating material from the body.